<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      table {
        border: 1px solid #000;
        text-align: center;
        width: 240px;
      }
      th,
      td {
        border: 1px solid #000;
      }
      h3 {
        position: relative;
      }
    </style>
  </head>
  <body>
    <div id="app">
      <h3>小黑的礼物清单</h3>
      <p>礼物总数-计算属性：{{ total }} 个</p>
      <table>
        <tr>
          <th>名字</th>
          <th>数量</th>
        </tr>
        <tr v-for="(item, index) in list" :key="item.id">
          <td>{{ item.name }}</td>
          <td>{{ item.num }}个</td>
        </tr>
      </table>

      <!-- 目标：统计求和，求得礼物总数 -->
      <p>礼物总数-计算属性：{{ total }} 个</p>
      <p>礼物总数-计算属性：{{ total }} 个</p>
      <p>礼物总数-计算属性：{{ total }} 个</p>
      <hr />
      <hr />
      <p>礼物总数-函数：{{ totalFn() }} 个</p>
      <p>礼物总数-函数：{{ totalFn() }} 个</p>
      <p>礼物总数-函数：{{ totalFn() }} 个</p>
      <p>礼物总数-函数：{{ totalFn() }} 个</p>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <script>
      const app = new Vue({
        el: "#app",
        data: {
          // 现有的数据
          list: [
            { id: 1, name: "篮球", num: 1 },
            { id: 2, name: "玩具", num: 2 },
            { id: 3, name: "铅笔", num: 5 },
          ],
        },
        // 方法
        methods: {
          totalFn() {
            console.log("❌methods方法多个地方调用，就会触发多次");
            const res = this.list.reduce((sum, item) => sum + item.num, 0);
            return res;
          },
        },
        // 计算属性结构 - 性能更好 - 有缓存
        computed: {
          // 计算总数
          total() {
            console.log("🌈computed会缓存，可以在多个地方同时用");
            const res = this.list.reduce((sum, item) => sum + item.num, 0);
            // 记得返回结果
            return res;
          },
        },
      });
    </script>
  </body>
</html>
